In the use and development of pulsed laser systems, extensive research into laser operation and manipulation is required. For example, in laser isotope separation processes, it is desirable to be able to detect a laser pulse and to use the signal to trigger other operations. Laser pulse detectors which are commercially available are expensive and are applicable to relatively narrow wavelength bands, i.e., infrared, visible, ultraviolet, etc.
The laser pulse detectors commercially available are of several types--the pyroelectric detector, the photon drag detector, diode detector, photomultiplier, bolometer. The pyroelectric detector has a relatively low cost but exhibits a slow response which is unacceptable for applications in which the detector response is used to trigger other operations in a process. The pyroelectric detector produces an electric current that is proportional to the rate of change of its temperature.
Vacuum photo diode detectors, one type of photo diode detector, employ a cathode in an evacuated cell, which emits electrons when struck by light. An electric field applied between the cathode and anode accelerates the electrons and the current produced is a function of light power. It can be fast but works only at the UV and visible ranges.
Semiconductor photo diode detectors utilize two semiconductor materials in sandwich form with an electric field thereacross which generates a current flow when illuminated by light. This detector can be fast but is useful only from the near ultraviolet to near IR range.
The bolometer uses a short narrow strip covered with light absorbing material. The electrical resistance of the strip changes when light strikes it due to a change in the strip's temperature.
The photomultiplier tube is similar to the vacuum photodiode but accelerates the electrons in 2 or more stages providing an amplification of the original signal. It can be fast but it is expensive and limited to visible, UV and near IR.
The photon drag detector exhibits a fast response time but is expensive and is specific for relatively narrow wavelength bands. This detector has a semiconductor as its prime element. When laser light is transmitted through the semiconductor, an electric field is induced which is a function of the laser light power.
Although all of the above-described detectors find use in specific applications, they are not generally adaptable for use as comprehensive laser pulse detectors which would be inexpensive to build and provide fast responses.
Therefore, it is a primary object of this invention to provide a laser pulse detector which is inexpensive to manufacture and is capable of detecting laser light of any wavelength.
Another object of this invention is to provide a laser pulse detector as in the above object in which the output signal has a very rapid rise time and may be used as a trigger pulse in laser utilization systems.